In the mid-19th century, conflicts over land, power, and national identity led to a war that changed the boundaries of both Mexico and the United States. It marked the first time America had sent thousands of soldiers to fight on foreign soil or occupied a foreign capital, and it served as a training ground for many generals who would later lead Confederate and Union troops in the Civil War. This four-part series tells the story of the U.S.-Mexican War from multiple perspectives, with prominent historians from both countries examining the conflict and its legacy.